Webster moves to Burton in a permanent transfer after spending last season on-loan with Heerenveen.
The midfielder is reunited with former Chelsea U21 coach Mark Robinson, who was named manager at Burton earlier this month.
Webster said: "I think it's a great time to be a Brewer. There's a lot happening at the club and I'm very excited to be a part of it.
"I always want to play at the level I know I can play at. Regular men's football is something I'm always aspiring to play and this is a really good stage for me to go and show what I can do.
"When I knew Mark Robinson was going to become Head Coach here it was a big thing for me. At Chelsea we had a great relationship. He's a guy who has really strong morals and values and really cares about his players which I think is the most important thing."
Burton Albion Sporting Director Bendik Hareide also told the club's website: "We are very pleased to have Charlie Webster on board. He is a talented midfielder with creative skills and goal-scoring abilities.
"Charlie's addition brings a new dynamic to our squad, and we are really looking forward to seeing him in action for Burton Albion."